How do we do that? We got to know the expectation of the audience and what we want to convey. Over emphasizing something or emphasizing meager issues may dilute the effect of conversation. We develop this skill with experience, paying attention to the audience and listening how others do it.

Certainly there are key things that you want to emphasize. Make sure what you want to emphasize is really relevant and audience has some clue about what you are talking.

Notice how you emphasize? Do you find yourself keep repeating what you want to communicate in different phrases or you cleverly divert every topic discussed and then associate to what you have in mind?

Observe if you are getting your point across. Use some relevant example to explain your point. Do not give frustrated look. You may have to do more work to refine your point.